Frequently Asked Questions

Frequently Asked Questions

General Information

Do Skylights Increase Heat?

Light and heat go together, so our job in the skylight industry is to manufacture products that let through lots of daylight but limit the amount of heat transfer in and out of skylights. The factors that affect the amount of heat that will travel to the room level include:

  • the roof orientation (eg north or west facing),
  • how far the light has to travel (eg the shaft height),
  • the type of glazing used at roof level and ceiling level,
  • the type of shaft, and
  • the penetration size.

Within our product ranges there are a number of skylight options to choose from to help combat any heat transfer, such as:

  • the type of glazing that is used at the roof level,
  • the coating on the glazing,
  • the type of glazing used at the ceiling level, and
  • accessories such as blockout blinds or dimmers

Different options can assist in reducing the chance of your skylight transmitting heat.  Take advantage of one of our in-home consultants or phone our office to discuss your particular situation. 

Can you ventilate skylights?

Yes. We can ventilate sklights. We can just ventilate them at the roof level so that they can “breathe” for example, to let hot air out of the shaft. We can also ventilate them at ceiling level to allow airflow out of the room up through the shaft and out the top structure to the surrounding atmosphere. There are ventilation options available for our SkyTunnel, Velux, and Atlite ranges. We can also add mechanical ventilation to skylights so that you can actively draw air out of the room.  This is done by adding a powered exhaust fan.

Are round skylights better than square skylights?

There is no short answer to this question!! Assuming that the skylight top structure has an opening that is matched by the ceiling opening and the connecting duct (for example 500mm diameter all the way through for a round or 500x500mm dimensions all the way through for a square), the following factors need to be taken into account:

  • Light surface area
  • Type of plastics or glass used in the roof top structure and at the ceiling level
  • Type of duct used to connect the roof top structure to the ceiling frame and panel

Light surface area – the bigger the surface area of the opening, the more light that can potentially be captured by the top structure.
Types of plastics or glass used in the skylight – traditionally square skylights have been manufactured using opalite domes which have a milky appearance. These are used to reduce the likelihood of heat transfer at the roof level and to give the light a whiter appearance. Because round skylights in a similar size have a smaller light surface area (eg the 500mm round doesn’t have the extra corner areas that a 500x500mm square has), manufacturers have tended to use clear acrylics or polycarbonates to compensate for the lower light surface area. In tubular daylighting devices, the clear plastics used in roof top structures are sometimes enhanced with special lenses that help capture low level light to maximise the light transfer down to the shaft.
Type of duct – please also see our comments in the specific FAQ about skylight ducts. If highly reflective rigid duct is used (such as in tubular daylighting devices), reflectivity is about 98% so almost all of the light captured at the roof level is transferred to the ceiling. Because of this higher level of reflectivity it is often possible to select a smaller diameter skylight as the increase in reflectivity compensates for the lower light surface area.
When comparing similar sizes of round and square skylights it often comes down to personal preference for the shape that matches your room or other ceiling fittings, particularly if you are considering a skylight that uses flexible duct.

Do your Skylights have a Warranty?

Yes, all of our skylights have a manufacturer’s warranty.   Please refer to the specific product on our website to see what is offered.
For installations by RJ Group WA, we guarantee our installations for a period of two (2) years from the date of installation.
If you believe you have a warranty issue, please contact us immediately so that we can come out and investigate any problems.

How Much Light will a Skylight Add to my Room?

There are lots of variables that can impact on the amount of light that can be generated by a skylight. These include:

  • Time of the year
  • Time of day
  • Surface area of the skylight (throat size)
  • Length of the shaft
  • Type of shaft
  • Type of glazing at roof and ceiling level
  • Orientation of the roof (eg. north vs south)
  • Size of the room
  • Decor in the room (eg light walls will help bounce the light around the room)
  • Ambient light levels (eg overcast vs sunny; trees, buildings or upper storeys that may impact on light)
Are there any Australian Skylight Standards?

Yes.  AS 4285-2019 is the Australian standard for skylights.  It specifies the requirements for manufacture and testing of rooflights.  It includes requirements for materials, fastenings and hardware, weatherproofing, ventilation, safety labels, marking and maintenance for rooflights.  At RJ Group WA, all of the products we sell are tested to meet AS 4285.

Is there an Industry Association?

RJ Group WA (RJ Skylights) is proud to be a founding member of the Skylight Industry Association of Australia. We abide by their Code of Conduct and actively contribute to the development of standards and technical improvement in the industry.


Can I have an electric light in my skylight?

Yes there are electric light options for skylights.

Can you get blinds for your skylight?

Yes we have a range of manual blockout blinds, electric and solar powered blinds, and dimmers for our different product ranges. They allow you to adjust the amount of light coming in through your skylight, whether it’s from the sun or the moon!

Light shafts and ducts

Does it matter what type of shaft you choose for your skylight?

Yes. The type of shaft under your skylight affects the intensity and quality of light that you can achieve at ceiling level.

If you install flexible duct, it needs to be pulled as taut as possible to enable the light to transmit from top to bottom. We work on a rule of thumb of about 65-70% light transmission on a well-installed flexible duct. There is also a difference in quality of flexible ducts – the more layers, the better for longevity and resistance to deterioration in your roof space. Our experience is that the cheaper products in the market use only 2 layer duct and so they deteriorate quite quickly.  Make sure you use flexible ducting that is made specially for skylights so that it reflects light – don’t buy duct that is made for exhaust applications as the light will not reflect down the duct.

Rigid highly reflective ducting has a mirrored surface which allows for maximum light transmission from roof to ceiling – our SkyTunnel product has about 98% light reflectivity in its rigid duct. The light generated is more white to look at and its intensity and quality is far superior to flexible duct particularly in the early mornings and late afternoons and on overcast days.

Under Velux skylights and Atlite roof windows we usually install a light shaft to match the ceiling – for example gyprock or timber lined. With gyprock, it is usually painted white to maximise light reflection down the shaft. These shafts are usually flared as well to help increase the spread of light. If you are doing a timber lining of your shaft the darker the timber colour, the less light reflection you will get off your shaft. However as this option is usually done on a raked ceiling, this does not have a big impact on the light you achieve.

My shaft is shredding or crumbling – why?

We see a number of light shafts that have been constructed out of corflute – this is a product that is a lightweight corrugated plastic. Over time moisture and sunlight cause damage to it and it starts to shred. You will see bits of plastic sitting on your diffuser. This will get worse over time. Depending on the size of the light shaft, the corflute could be replaced with a flexible duct, zinc alume or Colorbond metal sheets or gyprock.

Don’t Skylights Leak?

Sometimes! Old skylights with rusted flashings or sun damaged and cracked domes will inevitably start leaking when they reach a certain level of deterioration. Product maintenance is important to ensure that components that deteriorate over time are replaced or repaired. Roof maintenance to ensure that there is no build up of leaf or blossom matter around your skylight is also important so that there is no damming of water around the skylight.

If you are buying a new product choose one that has been tested to the Australian Standard AS 4285 so that it meets driven-rain and wind speed requirements. Make sure you are having your skylight installed by an experienced installer from a reputable business. You are cutting a hole in your roof to fit the skylight so you need to make sure that it is flashed and sealed correctly for the type or roof you have.

RJ Group WA has been in the skylight business for nearly 50 years. Our business has been built on ensuring our customers are satisfied and providing back-up for them in the long term. If you deal with us, you know that we will be around to help you if there is a problem down the track. Any business or installer that tells you they have never had a leak is not being truthful. Occasionally there will be an installation where there is a leak. It could be something as simple as being caused by weather coming from an unusual direction. Our aim is for a leak-free installation – if you do have an issue with our installation, we will ensure that we will make whatever adjustment is required to fix the problem. We provide a two year guarantee on our installations, double what most of our competitors offer.  In our view, two years will cover most weather patterns that you are likely to experience in Perth so that you can have peace-of-mind that your skylight will be leak-free.